1. Field of the Invention
The present invention relates to bone implants and, in particular, to a threaded dental implant with improved osseointegration.
2. Description of the Related Art
Dental implants are commonly used as anchoring members for dental restorations to provide prosthetic teeth at one or more edentulous sites in a patient's dentition at which the patient's original teeth have been lost or damaged. Typically, known implant systems include a dental implant made from a suitable biocompatible material, such as titanium. The dental implant is typically threaded into a bore which is drilled into the patient's mandible or maxilla at the edentulous site. The implant provides an anchoring member for a dental abutment, which in turn provides an interface between the implant and a dental restoration. The restoration is typically a porcelain crown fashioned according to known methods.
Many current dental implant surgeries are performed in two stages. In the initial or first stage, an incision is made in the patient's gingiva at an edentulous side, and a bore is drilled into the patient's mandible or maxilla at the edentulous site, followed by threading or impacting a dental implant into the bore using a suitable driver. Thereafter, a cap is fitted onto the implant to close the abutment coupling structure of the implant, and the gingiva is sutured over the implant. Over a period of several months, the patient's jaw bone grows around the implant to securely anchor the implant in the surrounding bone, a process known as osseointegration.
In a second stage of the procedure following osseointegration, the dentist reopens the gingiva at the implant site and secures an abutment and optionally, a temporary prosthesis or temporary healing member, to the implant. Then, a suitable permanent prosthesis or crown is fashioned, such as from one or more impressions taken of the abutment and the surrounding gingival tissue and dentition. In the final stage, the temporary prosthesis or healing member is removed and replaced with the permanent prosthesis, which is attached to the abutment with cement or with a fastener, for example. Alternative single stage implants with integral emergence profiles or one-piece implants with integral abutments may be used that extend through the transgingival layer so that the gingiva need not be reopened to access the implant.
Patients prefer to leave after initial surgery with some type of restoration and healing of both soft and hard tissue may be improved if the implant is loaded after surgery. Post-surgical loading, even if less than a full load of occlusion, however, is sufficient to displace the implant. Thus, threads may be used to secure the implant directly to the bone to achieve initial stability.
One way to improve osseointegration onto an implant, and in turn improve the long term stability of the implant, is to provide a porous material on the implant that the bone can grow into. Such a porous material may also increase short term stability for immediate loading due to a large friction coefficient with surrounding bone. Providing a porous material only on the surface of the implant, however, results in bone growth only near the surface of the implant. The final stability of the implant would be significantly increased if bone growth extends deeper than just near the surface of the implant. Such a porous structure, however, may not provide sufficient strength to use as threads on a screw-type implant to resist mastication forces. Thus, a porous implant is desired that provides sufficient initial and long-term stability when embedded in biological tissue, such as bone.